1. Technical Field
The present invention generally relates to an image processing program, an image processing apparatus, and an image processing method. In particular, the invention relates to a technique for suppressing see-through photo-optical appearance of any reverse-side image on the front of a reproduced copy, which typically occurs in copying.
2. Related Art
It is known in the art that a phenomenon of so-called “see-through photo-optical image appearance” may occur when the front of a sheet of original document is read optically. The see-through photo-optical image appearance is an undesirable phenomenon of photo-optical appearance of an image or the like that is actually printed on the back of a sheet of original document but scanned as a see-through image, which is not supposed to be, together with an image or the like that is printed on the front of the sheet when the front of the sheet is scanned for copying. When such a phenomenon happens, the reverse-side see-through image appears in a faint color or grayscale on a print copy.
To provide a solution to such a phenomenon, a technique for suppressing reverse-side see-through image components by using a weighted addition method is disclosed in JP-A-10-304204. In the related art disclosed in JP-A-10-304204, image data that is acquired by scanning the front of a sheet of original document is added to inverse reverse-side image data, which is acquired by reversing image data acquired by scanning the back of the sheet, while weighting them.
As another solution to the above phenomenon, a technique for suppressing reverse-side see-through image components and background components (i.e., color components of a sheet of paper itself) is disclosed in JP-A-2005-277886. In the related art disclosed in JP-A-2005-277886, measurement is carried out to obtain the frequency distribution of tone values of image data that is acquired by scanning the front of a sheet of original document. One of predetermined threshold values is selected on the basis of a tone value corresponding to a halftone peak. The selected threshold value is used for binarization. By this means, reverse-side see-through image components and background components are suppressed.